/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */
package java.util.stream;

import java.util.LongSummaryStatistics;
import java.util.Objects;
import java.util.OptionalDouble;
import java.util.OptionalLong;
import java.util.PrimitiveIterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.IntFunction;
import java.util.function.LongBinaryOperator;
import java.util.function.LongConsumer;
import java.util.function.LongFunction;
import java.util.function.LongPredicate;
import java.util.function.LongToDoubleFunction;
import java.util.function.LongToIntFunction;
import java.util.function.LongUnaryOperator;
import java.util.function.ObjLongConsumer;
import java.util.function.Supplier;

/**
 * Abstract base class for an intermediate pipeline stage or pipeline source
 * stage implementing whose elements are of type {@code long}.
 *
 * @param <E_IN> type of elements in the upstream source
 * @since 1.8
 */
abstract class LongPipeline<E_IN>
    extends AbstractPipeline<E_IN, Long, LongStream>
    implements LongStream {

  /**
   * Constructor for the head of a stream pipeline.
   *
   * @param source {@code Supplier<Spliterator>} describing the stream source
   * @param sourceFlags the source flags for the stream source, described in {@link StreamOpFlag}
   * @param parallel {@code true} if the pipeline is parallel
   */
  LongPipeline(Supplier<? extends Spliterator<Long>> source,
      int sourceFlags, boolean parallel) {
    super(source, sourceFlags, parallel);
  }

  /**
   * Constructor for the head of a stream pipeline.
   *
   * @param source {@code Spliterator} describing the stream source
   * @param sourceFlags the source flags for the stream source, described in {@link StreamOpFlag}
   * @param parallel {@code true} if the pipeline is parallel
   */
  LongPipeline(Spliterator<Long> source,
      int sourceFlags, boolean parallel) {
    super(source, sourceFlags, parallel);
  }

  /**
   * Constructor for appending an intermediate operation onto an existing pipeline.
   *
   * @param upstream the upstream element source.
   * @param opFlags the operation flags
   */
  LongPipeline(AbstractPipeline<?, E_IN, ?> upstream, int opFlags) {
    super(upstream, opFlags);
  }

  /**
   * Adapt a {@code Sink<Long> to an {@code LongConsumer}, ideally simply
   * by casting.
   */
  private static LongConsumer adapt(Sink<Long> sink) {
    if (sink instanceof LongConsumer) {
      return (LongConsumer) sink;
    } else {
      if (Tripwire.ENABLED) {
        Tripwire.trip(AbstractPipeline.class,
            "using LongStream.adapt(Sink<Long> s)");
      }
      return sink::accept;
    }
  }

  /**
   * Adapt a {@code Spliterator<Long>} to a {@code Spliterator.OfLong}.
   *
   * @implNote The implementation attempts to cast to a Spliterator.OfLong, and throws an exception
   * if this cast is not possible.
   */
  private static Spliterator.OfLong adapt(Spliterator<Long> s) {
    if (s instanceof Spliterator.OfLong) {
      return (Spliterator.OfLong) s;
    } else {
      if (Tripwire.ENABLED) {
        Tripwire.trip(AbstractPipeline.class,
            "using LongStream.adapt(Spliterator<Long> s)");
      }
      throw new UnsupportedOperationException("LongStream.adapt(Spliterator<Long> s)");
    }
  }

  // Shape-specific methods

  @Override
  final StreamShape getOutputShape() {
    return StreamShape.LONG_VALUE;
  }

  @Override
  final <P_IN> Node<Long> evaluateToNode(PipelineHelper<Long> helper,
      Spliterator<P_IN> spliterator,
      boolean flattenTree,
      IntFunction<Long[]> generator) {
    return Nodes.collectLong(helper, spliterator, flattenTree);
  }

  @Override
  final <P_IN> Spliterator<Long> wrap(PipelineHelper<Long> ph,
      Supplier<Spliterator<P_IN>> supplier,
      boolean isParallel) {
    return new StreamSpliterators.LongWrappingSpliterator<>(ph, supplier, isParallel);
  }

  @Override
  @SuppressWarnings("unchecked")
  final Spliterator.OfLong lazySpliterator(Supplier<? extends Spliterator<Long>> supplier) {
    return new StreamSpliterators.DelegatingSpliterator.OfLong(
        (Supplier<Spliterator.OfLong>) supplier);
  }

  @Override
  final void forEachWithCancel(Spliterator<Long> spliterator, Sink<Long> sink) {
    Spliterator.OfLong spl = adapt(spliterator);
    LongConsumer adaptedSink = adapt(sink);
    do {
    } while (!sink.cancellationRequested() && spl.tryAdvance(adaptedSink));
  }

  @Override
  final Node.Builder<Long> makeNodeBuilder(long exactSizeIfKnown, IntFunction<Long[]> generator) {
    return Nodes.longBuilder(exactSizeIfKnown);
  }

  // LongStream

  @Override
  public final PrimitiveIterator.OfLong iterator() {
    return Spliterators.iterator(spliterator());
  }

  @Override
  public final Spliterator.OfLong spliterator() {
    return adapt(super.spliterator());
  }

  // Stateless intermediate ops from LongStream

  @Override
  public final DoubleStream asDoubleStream() {
    return new DoublePipeline.StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Double> sink) {
        return new Sink.ChainedLong<Double>(sink) {
          @Override
          public void accept(long t) {
            downstream.accept((double) t);
          }
        };
      }
    };
  }

  @Override
  public final Stream<Long> boxed() {
    return mapToObj(Long::valueOf);
  }

  @Override
  public final LongStream map(LongUnaryOperator mapper) {
    Objects.requireNonNull(mapper);
    return new StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Long> sink) {
        return new Sink.ChainedLong<Long>(sink) {
          @Override
          public void accept(long t) {
            downstream.accept(mapper.applyAsLong(t));
          }
        };
      }
    };
  }

  @Override
  public final <U> Stream<U> mapToObj(LongFunction<? extends U> mapper) {
    Objects.requireNonNull(mapper);
    return new ReferencePipeline.StatelessOp<Long, U>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<U> sink) {
        return new Sink.ChainedLong<U>(sink) {
          @Override
          public void accept(long t) {
            downstream.accept(mapper.apply(t));
          }
        };
      }
    };
  }

  @Override
  public final IntStream mapToInt(LongToIntFunction mapper) {
    Objects.requireNonNull(mapper);
    return new IntPipeline.StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Integer> sink) {
        return new Sink.ChainedLong<Integer>(sink) {
          @Override
          public void accept(long t) {
            downstream.accept(mapper.applyAsInt(t));
          }
        };
      }
    };
  }

  @Override
  public final DoubleStream mapToDouble(LongToDoubleFunction mapper) {
    Objects.requireNonNull(mapper);
    return new DoublePipeline.StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Double> sink) {
        return new Sink.ChainedLong<Double>(sink) {
          @Override
          public void accept(long t) {
            downstream.accept(mapper.applyAsDouble(t));
          }
        };
      }
    };
  }

  @Override
  public final LongStream flatMap(LongFunction<? extends LongStream> mapper) {
    return new StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SORTED | StreamOpFlag.NOT_DISTINCT | StreamOpFlag.NOT_SIZED) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Long> sink) {
        return new Sink.ChainedLong<Long>(sink) {
          @Override
          public void begin(long size) {
            downstream.begin(-1);
          }

          @Override
          public void accept(long t) {
            try (LongStream result = mapper.apply(t)) {
              // We can do better that this too; optimize for depth=0 case and just grab spliterator and forEach it
              if (result != null) {
                result.sequential().forEach(i -> downstream.accept(i));
              }
            }
          }
        };
      }
    };
  }

  @Override
  public LongStream unordered() {
    if (!isOrdered()) {
      return this;
    }
    return new StatelessOp<Long>(this, StreamShape.LONG_VALUE, StreamOpFlag.NOT_ORDERED) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Long> sink) {
        return sink;
      }
    };
  }

  @Override
  public final LongStream filter(LongPredicate predicate) {
    Objects.requireNonNull(predicate);
    return new StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        StreamOpFlag.NOT_SIZED) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Long> sink) {
        return new Sink.ChainedLong<Long>(sink) {
          @Override
          public void begin(long size) {
            downstream.begin(-1);
          }

          @Override
          public void accept(long t) {
            if (predicate.test(t)) {
              downstream.accept(t);
            }
          }
        };
      }
    };
  }

  @Override
  public final LongStream peek(LongConsumer action) {
    Objects.requireNonNull(action);
    return new StatelessOp<Long>(this, StreamShape.LONG_VALUE,
        0) {
      @Override
      Sink<Long> opWrapSink(int flags, Sink<Long> sink) {
        return new Sink.ChainedLong<Long>(sink) {
          @Override
          public void accept(long t) {
            action.accept(t);
            downstream.accept(t);
          }
        };
      }
    };
  }

  // Stateful intermediate ops from LongStream

  @Override
  public final LongStream limit(long maxSize) {
    if (maxSize < 0) {
      throw new IllegalArgumentException(Long.toString(maxSize));
    }
    return SliceOps.makeLong(this, 0, maxSize);
  }

  @Override
  public final LongStream skip(long n) {
    if (n < 0) {
      throw new IllegalArgumentException(Long.toString(n));
    }
    if (n == 0) {
      return this;
    } else {
      return SliceOps.makeLong(this, n, -1);
    }
  }

  @Override
  public final LongStream sorted() {
    return SortedOps.makeLong(this);
  }

  @Override
  public final LongStream distinct() {
    // While functional and quick to implement, this approach is not very efficient.
    // An efficient version requires a long-specific map/set implementation.
    return boxed().distinct().mapToLong(i -> (long) i);
  }

  // Terminal ops from LongStream

  @Override
  public void forEach(LongConsumer action) {
    evaluate(ForEachOps.makeLong(action, false));
  }

  @Override
  public void forEachOrdered(LongConsumer action) {
    evaluate(ForEachOps.makeLong(action, true));
  }

  @Override
  public final long sum() {
    // use better algorithm to compensate for intermediate overflow?
    return reduce(0, Long::sum);
  }

  @Override
  public final OptionalLong min() {
    return reduce(Math::min);
  }

  @Override
  public final OptionalLong max() {
    return reduce(Math::max);
  }

  @Override
  public final OptionalDouble average() {
    long[] avg = collect(() -> new long[2],
        (ll, i) -> {
          ll[0]++;
          ll[1] += i;
        },
        (ll, rr) -> {
          ll[0] += rr[0];
          ll[1] += rr[1];
        });
    return avg[0] > 0
        ? OptionalDouble.of((double) avg[1] / avg[0])
        : OptionalDouble.empty();
  }

  @Override
  public final long count() {
    return map(e -> 1L).sum();
  }

  @Override
  public final LongSummaryStatistics summaryStatistics() {
    return collect(LongSummaryStatistics::new, LongSummaryStatistics::accept,
        LongSummaryStatistics::combine);
  }

  @Override
  public final long reduce(long identity, LongBinaryOperator op) {
    return evaluate(ReduceOps.makeLong(identity, op));
  }

  @Override
  public final OptionalLong reduce(LongBinaryOperator op) {
    return evaluate(ReduceOps.makeLong(op));
  }

  @Override
  public final <R> R collect(Supplier<R> supplier,
      ObjLongConsumer<R> accumulator,
      BiConsumer<R, R> combiner) {
    BinaryOperator<R> operator = (left, right) -> {
      combiner.accept(left, right);
      return left;
    };
    return evaluate(ReduceOps.makeLong(supplier, accumulator, operator));
  }

  @Override
  public final boolean anyMatch(LongPredicate predicate) {
    return evaluate(MatchOps.makeLong(predicate, MatchOps.MatchKind.ANY));
  }

  @Override
  public final boolean allMatch(LongPredicate predicate) {
    return evaluate(MatchOps.makeLong(predicate, MatchOps.MatchKind.ALL));
  }

  @Override
  public final boolean noneMatch(LongPredicate predicate) {
    return evaluate(MatchOps.makeLong(predicate, MatchOps.MatchKind.NONE));
  }

  @Override
  public final OptionalLong findFirst() {
    return evaluate(FindOps.makeLong(true));
  }

  @Override
  public final OptionalLong findAny() {
    return evaluate(FindOps.makeLong(false));
  }

  @Override
  public final long[] toArray() {
    return Nodes.flattenLong((Node.OfLong) evaluateToArrayNode(Long[]::new))
        .asPrimitiveArray();
  }

  //

  /**
   * Source stage of a LongPipeline.
   *
   * @param <E_IN> type of elements in the upstream source
   * @since 1.8
   */
  static class Head<E_IN> extends LongPipeline<E_IN> {

    /**
     * Constructor for the source stage of a LongStream.
     *
     * @param source {@code Supplier<Spliterator>} describing the stream source
     * @param sourceFlags the source flags for the stream source, described in {@link StreamOpFlag}
     * @param parallel {@code true} if the pipeline is parallel
     */
    Head(Supplier<? extends Spliterator<Long>> source,
        int sourceFlags, boolean parallel) {
      super(source, sourceFlags, parallel);
    }

    /**
     * Constructor for the source stage of a LongStream.
     *
     * @param source {@code Spliterator} describing the stream source
     * @param sourceFlags the source flags for the stream source, described in {@link StreamOpFlag}
     * @param parallel {@code true} if the pipeline is parallel
     */
    Head(Spliterator<Long> source,
        int sourceFlags, boolean parallel) {
      super(source, sourceFlags, parallel);
    }

    @Override
    final boolean opIsStateful() {
      throw new UnsupportedOperationException();
    }

    @Override
    final Sink<E_IN> opWrapSink(int flags, Sink<Long> sink) {
      throw new UnsupportedOperationException();
    }

    // Optimized sequential terminal operations for the head of the pipeline

    @Override
    public void forEach(LongConsumer action) {
      if (!isParallel()) {
        adapt(sourceStageSpliterator()).forEachRemaining(action);
      } else {
        super.forEach(action);
      }
    }

    @Override
    public void forEachOrdered(LongConsumer action) {
      if (!isParallel()) {
        adapt(sourceStageSpliterator()).forEachRemaining(action);
      } else {
        super.forEachOrdered(action);
      }
    }
  }

  /**
   * Base class for a stateless intermediate stage of a LongStream.
   *
   * @param <E_IN> type of elements in the upstream source
   * @since 1.8
   */
  abstract static class StatelessOp<E_IN> extends LongPipeline<E_IN> {

    /**
     * Construct a new LongStream by appending a stateless intermediate
     * operation to an existing stream.
     *
     * @param upstream The upstream pipeline stage
     * @param inputShape The stream shape for the upstream pipeline stage
     * @param opFlags Operation flags for the new stage
     */
    StatelessOp(AbstractPipeline<?, E_IN, ?> upstream,
        StreamShape inputShape,
        int opFlags) {
      super(upstream, opFlags);
      assert upstream.getOutputShape() == inputShape;
    }

    @Override
    final boolean opIsStateful() {
      return false;
    }
  }

  /**
   * Base class for a stateful intermediate stage of a LongStream.
   *
   * @param <E_IN> type of elements in the upstream source
   * @since 1.8
   */
  abstract static class StatefulOp<E_IN> extends LongPipeline<E_IN> {

    /**
     * Construct a new LongStream by appending a stateful intermediate
     * operation to an existing stream.
     *
     * @param upstream The upstream pipeline stage
     * @param inputShape The stream shape for the upstream pipeline stage
     * @param opFlags Operation flags for the new stage
     */
    StatefulOp(AbstractPipeline<?, E_IN, ?> upstream,
        StreamShape inputShape,
        int opFlags) {
      super(upstream, opFlags);
      assert upstream.getOutputShape() == inputShape;
    }

    @Override
    final boolean opIsStateful() {
      return true;
    }

    @Override
    abstract <P_IN> Node<Long> opEvaluateParallel(PipelineHelper<Long> helper,
        Spliterator<P_IN> spliterator,
        IntFunction<Long[]> generator);
  }
}
